The present invention relates generally to an apparatus for removably combining a tool such as an annular cutter with a hand, electric, or pneumatic power driver.
Electric and pneumatic tool drivers such as drills are well known. Although drill bits are the most common tools used with such drivers, other tools used with power drivers include nut drivers, burrs, mounted grinding stones, and other cutting or abrading tools. Since the tool shanks (shafts) vary in diameter or have a polygonal cross-section, tool drivers usually have an adjustable chuck for receiving the variously sized tools. The chuck may be attached to the driver spindle by a threaded or tapered bore. Examples of these types of chucks are disclosed in U.S. Pat. Nos. 6,533,291, 5,125,673, and 5,354,075.
Typically, a chuck includes three gripping members disposed approximately 120 degrees apart from each other. The members are configured so that their center lines meet at a point along the chuck's central axis. The three gripping members are movable radially in a linear motion to grip the cylindrical or polygonal tool shank displaced approximately along the chuck's center axis. The chuck is attached to the spindle of a driver and is configured so that rotation of the chuck's body in one direction forces the gripping members into a gripping relationship with the tool shank, while rotation in the opposite direction releases the gripping relationship. The chuck may be operated by a chuck key or the sleeve may be rotated by hand in a keyless configuration.
One problem with traditional chucks and other keyless arbors provided on tools such as magnetic base drills is that the linear movement of the gripping members requires the chuck or keyless arbor drive mechanism to have a large diameter relative to the arbor in order to accommodate the travel distance of the gripping members. Large diameter chucks are unfavorable because they reduce the vertical travel capacity of the power drivers or increase the overall height of the power driver when used in applications such as magnetic base drills. Another problem with existing chucks is that they grip only on the outer diameter of the shank, whereas many cutting tools such as annular cutters are driven by flats provided on the cutting tool shank. Generally the depth of the flats provided on the cutting tool shank will vary from cutter to cutter and from manufacturer to manufacturer. In many existing keyless arbor designs, if the shank of the cutting tool is not produced in an exact manner, the gripping or driving members of the arbor will not accurately engage because the locked position of the drive mechanism has a fixed (non-variable) position thereby causing the cutting tool to be loose in the arbor or not allowing the drive mechanism to realize its fully locked position. This has led to the production of many specialized tools for use only in specific brands of drivers.